// Copyright 2016 The Draco Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
#ifndef DRACO_COMPRESSION_ATTRIBUTES_PREDICTION_SCHEMES_PREDICTION_SCHEME_DELTA_DECODER_H_
#define DRACO_COMPRESSION_ATTRIBUTES_PREDICTION_SCHEMES_PREDICTION_SCHEME_DELTA_DECODER_H_

#include "draco/compression/attributes/prediction_schemes/prediction_scheme_decoder.h"

namespace draco {

// Decoder for values encoded with delta coding. See the corresponding encoder
// for more details.
template <typename DataTypeT, class TransformT>
class PredictionSchemeDeltaDecoder
    : public PredictionSchemeDecoder<DataTypeT, TransformT> {
  public:
    using CorrType =
        typename PredictionSchemeDecoder<DataTypeT, TransformT>::CorrType;
    // Initialized the prediction scheme.
    explicit PredictionSchemeDeltaDecoder(const PointAttribute *attribute)
        : PredictionSchemeDecoder<DataTypeT, TransformT>(attribute) {}
    PredictionSchemeDeltaDecoder(const PointAttribute *attribute,
                                 const TransformT &transform)
        : PredictionSchemeDecoder<DataTypeT, TransformT>(attribute, transform) {}

    bool ComputeOriginalValues(const CorrType *in_corr, DataTypeT *out_data,
                               int size, int num_components,
                               const PointIndex *entry_to_point_id_map) override;
    PredictionSchemeMethod GetPredictionMethod() const override {
        return PREDICTION_DIFFERENCE;
    }
    bool IsInitialized() const override {
        return true;
    }
};

template <typename DataTypeT, class TransformT>
bool PredictionSchemeDeltaDecoder<DataTypeT, TransformT>::ComputeOriginalValues(
    const CorrType *in_corr, DataTypeT *out_data, int size, int num_components,
    const PointIndex *) {
    this->transform().Initialize(num_components);
    // Decode the original value for the first element.
    std::unique_ptr<DataTypeT[]> zero_vals(new DataTypeT[num_components]());
    this->transform().ComputeOriginalValue(zero_vals.get(), in_corr, out_data);

    // Decode data from the front using D(i) = D(i) + D(i - 1).
    for (int i = num_components; i < size; i += num_components) {
        this->transform().ComputeOriginalValue(out_data + i - num_components,
                                               in_corr + i, out_data + i);
    }
    return true;
}

}  // namespace draco

#endif  // DRACO_COMPRESSION_ATTRIBUTES_PREDICTION_SCHEMES_PREDICTION_SCHEME_DELTA_DECODER_H_
